U.S. patent number 6,714,671 [Application Number 09/587,225] was granted by the patent office on 2004-03-30 for method of detecting pattern defects.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Koichi Wakitani, Noriaki Yukawa.
United States Patent |
6,714,671 |
Wakitani , et al. |
March 30, 2004 |
Method of detecting pattern defects
Abstract
An input subject pattern is compared with a good product pattern
that is registered beforehand, and a different portion of these is
detected as a defect pattern. The detected defect pattern is
classified in accordance with the features of the contour of the
defect pattern.
Inventors: |
Wakitani; Koichi (Osaka,
JP), Yukawa; Noriaki (Takaichi-gun, JP) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Osaka, JP)
|
Family
ID: |
15586390 |
Appl.
No.: |
09/587,225 |
Filed: |
June 2, 2000 |
Foreign Application Priority Data
|
|
|
|
|
Jun 2, 1999 [JP] |
|
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11-154535 |
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Current U.S.
Class: |
382/149; 382/145;
382/147; 382/199; 382/218 |
Current CPC
Class: |
G06T
7/0006 (20130101); G06T 7/001 (20130101); G06T
2207/30141 (20130101); G06T 2207/30148 (20130101) |
Current International
Class: |
G01B
11/30 (20060101); G01N 21/88 (20060101); G06K
9/48 (20060101); G06K 9/20 (20060101); G06T
7/00 (20060101); G06K 9/68 (20060101); G06K
9/00 (20060101); H01L 21/66 (20060101); G06K
009/00 (); G06K 009/48 (); G06K 009/68 () |
Field of
Search: |
;382/144,145,146,147,148,149,199,217,218,219,221 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wu; Jingge
Assistant Examiner: Hesseltine; Ryan J.
Attorney, Agent or Firm: Jordan and Hamburg LLP
Claims
What is claimed is:
1. A method of detecting pattern defects comprising: comparing an
image of an input subject pattern with an image of a good product
pattern that is registered beforehand; detecting a continuous
region of the subject pattern that does not overlap with the good
product pattern as a defect pattern; extracting a line segment of
the defect pattern that coincides with a contour of the subject
pattern; detecting all open end points of the line segment; and
detecting the defect pattern as a defect in which a pattern that
ought to be isolated is connected when the defect pattern contains
four or more of the open end points.
2. A method of detecting pattern defects comprising: comparing an
image of an input subject pattern with an image of a good product
pattern that is registered beforehand; detecting a continuous
region of the good product pattern that does not overlap with the
subject pattern as a defect pattern; extracting a line segment of
the defect pattern that coincides with a contour of the good
product pattern; detecting all open end points of the line segment;
detecting the defect pattern as a defect in which a pattern that
ought to be connected is isolated when the defect pattern contains
four or more of the open end points.
3. A method of detecting pattern defects comprising: comparing an
image of an input subject pattern with an image of a good product
pattern that is registered beforehand; detecting a continuous
region of the good product pattern that does not overlap with the
subject pattern as a defect pattern; extracting a line segment of
the defect pattern that coincides with a contour of the good
product pattern; detecting all open end points of the line segment;
detecting the defect pattern as a defect in which a region is
present projecting into a region where the input subject pattern
ought not to be present when the defect pattern contains two or
more of the open end points.
4. A method of detecting pattern defects comprising: comparing an
image of an input subject pattern with an image of a good product
pattern that is registered beforehand; detecting a continuous
region of the good product pattern that does not overlap with the
subject pattern as a defect pattern; extracting a line segment of
the defect pattern that coincides with a contour of the good
product pattern; detecting all open end points of the line segment;
detecting the defect pattern as a defect in which a region is
present projecting into a region where the good product pattern is
present when the defect pattern contains two or more of the open
end points.
5. The method of detecting pattern defects according to any one of
claims 1-4, wherein the pattern is a circuit pattern.
6. The method of detecting pattern defects according to any one of
claims 1-4, wherein the pattern is a semiconductor pattern.
7. The method of detecting pattern defects according to claim 6,
wherein the pattern is for liquid crystal display panels.
Description
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
In the examination of patterns such as the wiring patterns of
semiconductors, printed circuit boards, liquid crystals, or plasma
display panels etc or printed/impressed patterns, the present
invention relates to a method of detecting pattern defects whereby
defects are classified and detected.
2. Description of Related Art
Conventional methods of detecting pattern defects include the
design rule check (DRC) method and the comparison method. The DRC
method involves detecting the pattern line width and pattern
separation by image processing. If the detected line width or
pattern separation as respectively shown in FIG. 16A and FIG. 16B
is not in accordance with certain wiring or pattern rules, such is
determined as a pattern defect. In the example shown in FIGS. 16A
and 16B, the line width and the pattern separation are both smaller
than predetermined values, and therefore are detected as failures.
The comparison method involves comparing a subject image S that is
input with the previously registered image of a good product G, and
detecting the difference of these as a defect pattern D, as shown
in FIG. 17.
However, with the DRC method, as long as the detected line width or
pattern separation satisfies certain rules, the pattern is
determined normal. For example, in such a case as shown in FIGS.
18A and 18B, a bridge or a slit in the pattern cannot be detected
as defects. On the other hand, normal patterns may be detected as
failures if they contravene the pattern rules. For example, the
separation P shown in FIG. 19A or the line width Q shown in FIG.
19B may be detected as a pattern defect.
With the comparison method, minute differences between the subject
image and the registered image of a good product cannot be
distinguished from noise etc, and so minute defects cannot be
detected. Moreover, crucial defects such as a bridge D2 shown in
FIG. 20 cannot be differentiated from permissible defects such as
protuberance D1 shown in FIG. 20.
SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to
provide a method of detecting pattern defects that is capable of
classifying and reliably detecting various pattern defects.
A method of detecting pattern defects according to the resent
invention involves comparing an input subject pattern with a good
product pattern that is registered beforehand, in which a different
portion of the good product pattern and subject pattern is detected
as a defect pattern, and the defect pattern is classified and
detected in accordance with the features of the contour of the
defect pattern. Pattern defects of various types such as for
example bridges, breaks, residual patterns, missing patterns,
projection/protrusion, nicks/intrusion etc can reliably be detected
and classified.
While novel features of the invention are set forth in the
preceding, the invention, both as to organization and content, can
be further understood and appreciated, along with other objects and
features thereof, from the following detailed description and
examples when taken in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flow chart of a method of detecting pattern defects
according to one embodiment of the present invention;
FIG. 2A to FIG. 2E are diagrams given in explanation of detection
of a bridge defect;
FIG. 3A to FIG. 3E are diagrams given in explanation of detection
of a break defect ;
FIG. 4A to FIG. 4C are diagrams given in explanation of detection
of an island defect;
FIG. 5A to FIG. 5F are diagrams given in explanation of detection
of a pin hole defect or missing pattern;
FIG. 6A to FIG. 6E are diagrams given in explanation of detection
of a projection/protrusion defect;
FIG. 7A to FIG. 7E are diagrams given in explanation of detection
of a nick/intrusion defect;
FIG. 8 is a diagram of an image of a good product in image
processing in this embodiment;
FIG. 9 is a diagram of a subject image in image processing in this
embodiment;
FIG. 10 is a diagram of a comparison image in image processing in
this embodiment;
FIG. 11 is a diagram of a contour line relating exclusively to a
subject in image processing in this embodiment;
FIG. 12 is a diagram of contact points in image processing in this
embodiment;
FIG. 13 is a diagram showing the case of occurrence of two contact
points in image processing in this embodiment;
FIG. 14 is a diagram showing the case of occurrence of four contact
points in image processing in this embodiment; FIG. 15 is a diagram
of defect classification in image processing in this
embodiment;
FIGS. 16A and 16B are diagrams of the DRC method, which is a
conventional pattern defect detection method;
FIG. 17 is a diagram of the comparison method, which is another
conventional pattern defect detection method;
FIGS. 18A and 18B are diagrams of defects that cannot be detected
by the conventional DRC method;
FIGS. 19A and 19B are diagrams of good product patterns which are
detected as defects by the conventional DRC method; and
FIG. 20 is a diagram given in explanation of problems of the
conventional comparison method.
DESCRIPTION OF PREFERRED EMBODIMENTS
Preferred embodiments of a method of detecting pattern defects
according to the present invention are described below with
reference to FIG. 1 to FIG. 15.
FIG. 1 is a flow chart of a method of detecting pattern defects
according to this embodiment. The method comprises: a step of
inputting a subject pattern image; a step of comparing the subject
pattern image with the image of a good product pattern that has
been previously registered; a step of detecting outline points on
the contour of one or other of the good product pattern and the
subject pattern not overlapping with the other; a step of
extracting contact points from the outline points, which are not in
contact with two or more of the other outline points; a step of
detecting as a defect pattern a continuous region where there is no
mutual overlap between the subject pattern and the good product
pattern; a step of counting the number of contact points contained
in the defect pattern; and a step of classifying and detecting
defects in accordance with the number of the contact points. A
specific description is given below with reference to FIG. 2 to
FIG. 7.
FIGS. 2A through 2E show a case where a pattern defect is detected
as a bridge. FIG. 2A shows an input image B of a subject pattern 3
that is to be inspected and FIG. 2B shows an image A of a
corresponding good product pattern 1 that is registered beforehand.
FIG. 2C shows the contour 5 of a region of the subject pattern B
that does not overlap with the good product pattern A, detected by
comparing both images, and this region is determined as a defect
pattern. FIG. 2D shows the end points 7 of the contour 5 of the
defect pattern, as indicated by circles. The end points 7 are the
points on the contour 5 of the defect pattern that make point
contact with the good product pattern A, and these are determined
as contact points. FIG. 2E shows the detected defect pattern with
the contact points 7. Based on the fact that this defect pattern
contains four contact points, it is detected, for example, as a
bridge, or a "defect in which patterns which ought to be isolated
are connected."
FIGS. 3A through 3E show a case where a pattern defect is detected
as a break. FIG. 3A shows an input image A of a subject pattern 4
that is to be inspected and FIG. 3B shows an image B of a
corresponding good product pattern 2 that is registered beforehand.
FIG. 3C shows the contour 6 of a region of the good product pattern
B that does not overlap with the subject pattern A, detected by
comparing both images, and this region is determined as a defect
pattern. FIG. 3D shows the end points 8 of the contour 6 of the
defect pattern, as indicated by circles. The end points 8 are the
points at the ends of the contour 6 of a region of the good product
pattern B not overlapping the subject pattern A, that make point
contact with the subject pattern B, and these are determined as
contact points. FIG. 3E shows the detected defect pattern with the
contact points 8. Based on the fact that this defect pattern
contains four contact points, it is detected, for example, as a
break, or a "defect in which patterns which ought to be connected
are isolated."
FIGS. 4A through 4C show a case where a pattern defect is detected
as an island. FIG. 4A shows an input image B of a subject pattern
23 that is to be inspected and FIG. 4B shows an image A of a
corresponding good product pattern 21 that is registered
beforehand. FIG. 4C shows the contour 25 of a region of the subject
pattern B that does not overlap with the good product pattern A,
detected by comparing both images, and this region is determined as
a defect pattern. Since there are no end points in the contour 25
of the detected defect pattern that make contact with the good
product pattern A, the defect pattern is detected, for example, as
an island, or a "defect in which an isolated pattern exists in a
region in which no pattern ought to exist."
FIGS. 5A through 5C show a case where a defect is detected as
pattern missing. FIG. 5A shows an input image A of a subject
pattern 24 that is to be inspected and FIG. 5B shows an image B of
a corresponding good product pattern 22 that is registered
beforehand. FIG. 5C shows the contour 26 of a region of the good
product pattern B that does not overlap with the subject pattern A,
detected by comparing both images, and this region is determined as
a defect pattern. Since there are no end points in the contour 26
of the detected defect pattern that make contact with the subject
pattern A, the defect pattern is detected, for example, as a
pattern missing defect, or a "defect in which a pattern which ought
to exist in certain region does not exist."
FIGS. 5D through 5F show a case where a defect is detected as a pin
hole defect. FIG. 5D shows an input image A of a subject pattern
124 that is to be inspected and FIG. 5E shows an image B of a
corresponding good product pattern 122 that is registered
beforehand. FIG. 5F shows the contour 126 of a region of the good
product pattern B that does not overlap with the subject pattern A,
detected by comparing both images, and this region is determined as
a defect pattern. Since there are no end points in the contour 126
of the detected defect pattern that make contact with the subject
pattern A, the defect pattern is detected, for example, as a pin
hole defect, or a "defect in which a portion of a pattern is
missing."
FIGS. 6A through 6E show a case where a defect is detected as a
projection/protrusion pattern defect. FIG. 6A shows an input image
B of a subject pattern 33 that is to be inspected and FIG. 6B shows
an image A of a corresponding good product pattern 31 that is
registered beforehand. FIG. 6C shows the contour 35 of a region of
the subject pattern B that does not overlap with the good product
pattern A, detected by comparing both images, and this region is
determined as a defect pattern. FIG. 6D shows the end points 37 of
the contour 35 of the defect pattern, as indicated by circles. The
end points 37 are the points at the ends of the contour 35 of a
region of the subject pattern B not overlapping with the good
product pattern A, that make point contact with the good product
pattern A, and these are determined as contact points. FIG. 6E
shows the detected defect pattern with the contact points 37. Based
on the fact that this defect pattern contains two contact points,
it is detected, for example, as a projection/protrusion pattern
defect, or a "defect in which a portion of the pattern is present
projecting into a region where pattern ought not to be
present."
FIGS. 7A through 7E show a case where a defect is detected as a
nick/intrusion defect. FIG. 7A shows an input image A of a subject
pattern 34 that is to be inspected and FIG. 7B shows an image B of
a corresponding good product pattern 32 that is registered
beforehand. FIG. 7C shows the contour 36 of a region of the good
product pattern B that does not overlap with the subject pattern A,
detected by comparing both images, and this region is determined as
a defect pattern. FIG. 7D shows the end points 38 of the contour 36
of the defect pattern, as indicated by circles. The end points 38
are the points that are on the contour 36 of the defect pattern and
in contact with the good product pattern B, and these are
determined as contact points. FIG. 7E shows the detected defect
pattern with the contact points 38. Based on the fact that this
defect pattern contains two contact points, it is detected, for
example, as a nick/intrusion defect, or a "defect in which a region
other than a pattern is present projecting into a region where the
pattern ought to be present."
Next, the process whereby the method of defect detection described
above is performed by image processing will be described. FIG. 8
shows the image of a good product pattern and FIG. 9 shows the
image of a subject pattern. FIG. 10 shows an image obtained by
comparing these two images. In these Figures, pixels indicated by
the value 0 are pixels where neither the good product pattern nor
the subject pattern are present; pixels indicated by the value 1
are pixels where only the good product pattern is present; pixels
indicated by the value 2 are pixels where only the subject pattern
is present; and pixels indicated by the value 3 are pixels where
both the good product pattern and the subject pattern are
present.
In FIG. 11, the pixels denoted at encircled numeral 2 are pixels in
which only subject pattern is present and in which no subject
pattern is present at their peripheries; they therefore constitute
outline pixels or the contour of a region of the subject pattern
that does not overlap with the good product pattern. The regions
defined by these outline pixels are determined as defect patterns.
In FIG. 12, only the pixels that are not in contact with two or
more of the other outline pixels are denoted at encircled numeral
2, and they are determined as contact point pixels.
Referring now to FIG. 13, the two contact point pixels each contain
one contact point, indicated by black dots, that are the points in
the external contour of the contact point pixels and are in contact
with the adjacent pixels indicated by the value 3 where both the
good product pattern and the subject pattern are present. In FIG.
14, the contact point pixels denoted at encircled numeral 2 have
two contact points each, indicated by black dots, making a total of
four contact points. Consequently, the region X in FIG. 15 includes
a total of two contact points and so is classified in pattern
inspection as a defect in the form of a projection, whereas since
the region Y contains a total of four contact points, it is
classified in the pattern inspection as a bridge defect.
Although in the above embodiment the description has assumed that
the objects were circuit patterns or semiconductor patterns etc,
the present invention can also be applied to inspection of patterns
such as letters or symbols.
As will be clear from the above description, according to the
method of detecting pattern defects of the present invention, a
good product pattern is registered beforehand and the good product
pattern and an input subject pattern are compared, the difference
of these being detected as a defect pattern, and the type of defect
pattern is classified and detected in accordance with the features
of the contour of the defect pattern. Consequently, pattern defects
of various types such as for example bridges, breaks, residual
patterns, missing patterns, projection/protrusion, nicks/intrusion
etc can reliably be detected and classified.
Although the present invention has been fully described in
connection with the preferred embodiment thereof, it is to be noted
that various changes and modifications apparent to those skilled in
the art are to be understood as included within the scope of the
present invention as defined by the appended claims unless they
depart therefrom.
* * * * *